Breast cancer is a disease that kills over 45,000 women each year in the United States alone. Over 180,000 new cases of breast cancer are diagnosed annually, and it is estimated that one in eight women will develop breast cancer. These numbers indicate that breast cancer is one of the most dangerous diseases facing women today. Cancer research has been unable to determine the cause of breast cancer, and has not found a suitable method of therapy or prevention.
A woman diagnosed with breast cancer may be treated with surgery, hormone therapy, chemotherapy, and radiation. If the patient develops metastatic disease, radiation and high dose chemotherapy are required to ablate the cancer in remote areas such as the brain, bone, and liver.
The current therapies available for the treatment of breast cancer are toxic, dangerous, costly, and many are ineffective, especially in the treatment of metastatic disease. The table below was extracted from Churchill Livingston, Clinical Oncology, 1995, and summarizes data available on the current methods of treatment and expected survival rates.
Currently, there are no therapies that are effective for long term treatment of breast cancer that has metastasized to lymph nodes or distal sites. Local disease can be effectively treated by surgery, if all of the cancer can be removed. A new therapy for the effective treatment of breast cancer that could stop the growth of breast cancer and of cells derived from metastatic cancer is urgently needed. Such a therapy would be useful in the treatment of localized breast cancer, in long term treatment of metastatic disease, and as a follow-up treatment after surgical removal of tumors. Other applications include a growth inhibitor as a primary therapy and for preventative use.
Detection methods for breast cancer, such as mammogram, physical exam, CAT-scan, and ultrasound, have significantly improved early detection of breast cancer. However, with these methods, a suspected tumor must still be surgically removed for pathological examination to determine if the tumor is benign or malignant, and to attempt to determine the tissue type and grade of the malignancy. This pathological diagnosis helps to determine what subsequent treatment protocols may be used.
For breast cancer, these methods are generally inconclusive, as adequate breast cancer tumor markers are not available. Available markers such as CA 15-3 and CA 27-29 are used as indicators of metastases, however, they are not specific. There is a great need for diagnostic tools and methods that can effectively and reliably diagnose breast cancer, e.g., using new and specific breast cancer markers. In addition, a reliable and simple method for the early detection and diagnosis of breast cancer is greatly needed. Preferably, such an early detection method would identify breast cancer in its early stages, track progression of breast cancer through advanced metastatic disease, and diagnose the propensity of a patient to develop breast cancer or to develop advanced disease. Most preferably, the diagnostic method could be used without tissue biopsy, e.g., by analysis of a body fluid such as blood.
Human mammary tissues undergo a burst of proliferative activities at the onset of menarche and during each menstrual cycle. Studies on the effects of estrogen on mammary tissues and tumors indicate that estrogen is a primary growth-initiating factor for mammary tissues. Estradiol-sensitive growth factors have been characterized. In addition, mammary cell growth factors which are not hormonal in nature have also been described.
Specific growth factors which have been shown to have a stimulating effect on mammary tissue growth include platelet-derived growth factor (PDGF), insulin-like growth factor (IGF-1) and transforming growth factor (TGF) alpha. TGF-beta, on the other hand, has been shown to suppress mammary tissue growth.
The regulation of mammary cell growth is of great importance in the diagnosis and treatment of breast cancer. Neoplastic growth of mammary tissues, if unchecked, can develop into uncontrollably-proliferating malignant tumors, which are the cause of death of thousands of women yearly. A growth inhibition factor capable of specifically suppressing mammary cell growth would provide a dynamic tool for use in the diagnosis and treatment of breast cancer.
Thus, it would be of great utility to isolate and characterize a specific mammary cell growth inhibitor, to identify its nucleic acid sequence and amino acid sequence, and to recombinantly express the inhibitor as a purified protein. Diagnostic and therapeutic methods using the nucleic acid sequence and/or recombinantly produced inhibitor would be of great utility in the diagnosis and treatment of breast cancer.
A specific mammary cell growth inhibitor, Mammastatin, has been isolated from normal human mammary cells and characterized. It has now been found that Mammastatin is produced by normal mammary cells, but not by breast cancer cells. Furthermore, it has now been found that the reduction or absence of Mammastatin in the blood correlate with the presence of breast cancer. Administration of active Mammastatin prevents growth of breast cancer cells.
The nucleic acid sequence encoding Mammastatin has now been cloned, sequenced, and expressed recombinantly in host cells as an active inhibitor of mammary cell growth. The isolated and characterized nucleic acid sequence (Sequence ID No: 1) and its deduced amino acid sequence provide unique and specific tools for use in the diagnosis and treatment of breast cancer.
The present invention provides an isolated and purified nucleic acid sequence encoding Mammastatin, a specific protein inhibitor of mammary cell growth, and particularly of mammary cancer cell growth. The invention also includes plasmids and vectors containing the Mammastatin nucleic acid sequence, amino acid sequence of Mammastatin, and methods, kits, and compositions utilizing the Mammastatin nucleic acid or amino acid sequences to produce purified mammary cell growth inhibitor and in the diagnosis and treatment of breast cancer. The inventive compositions include probes and primers that specifically hybridize to the Mammastatin nucleic acid sequence and its RNA products.
The invention further includes a method for treating breast cancer by administering Mammastatin.